The long term goals of this project are to identify epitopes found in the filarial parasite Onchocera volvulus that may be used to elicit protective immunity, and to evaluate the utility of these epitopes for use as the basis of a vaccine against O. volvulus infection. O. volvulus is the causative agent of onchocerciasis, which is one of the major causes of blindness in the world today. Indirect evidence in humans, as well as direct evidence from related filarial infections suggests that it may be possible to elicit a protective immune response against infection by O. volvulus. In these related filarial infections, it has been found that a protective immune response may be induced by antigens found in the larval forms of the parasite. Recently, we have shown that it is possible to isolate cDNA clones that express antigens found in O. volvulus larvae from a cDNA library prepared form adult stage O. volvulus mRNA. The experiments described in this proposal are directed towards isolating and characterizing clones expressing epitopes that may correlate with immunity to O. volvulus infection. In order to accomplish this, the ability of sera from individuals with patent infections to immunoprecipitate in vitro translation products of adult O. volvulus mRNA will be compared to sera from exposed, but uninfected individuals. The results from this experiment will be used to select between five alternative screening strategies. These strategies will utilize sera and peripheral blood mononuclear cells from infected and exposed, but uninfected individuals as well as antisera prepared against larval and adult parasites. EAch of the clones will be characterized by Northern and Southern blot analysis, DNA sequence analysis, and identification of the native parasite antigen sharing epitopes with each of the recombinant fusion proteins. The major epitopes encoded by each of the potentially protective clones will be experimentally determined. The most reactive epitopes identified in this manner will be compared to each other, and to those predicted on theoretical grounds. Finally, the structure of the genes encoding antigens with unusual structural features will be examined. Eventually, the epitopes defined by this study may be used to test for the induction of a protective immune response in animal models of Onchocercal infection.